KR20040001324A - Position sensitive liquid crystal display device - Google Patents

Abstract

PURPOSE: A liquid crystal display for sensing a position is provided to remove a noise due to a short-circuit and signal interference between black matrices used as position sensing electrodes and a common electrode, thereby improving position sensing ability and the quality of a picture. CONSTITUTION: Gate lines and data lines are formed on a first substrate for defining pixel areas. Thin film transistors are formed at crossing areas of the gate lines and the data lines. At least one pair of a first metal layer and a second metal layer is formed in the pixel area. A passivation film(107) is accumulated on the first substrate. Black matrices(122) are formed at positions corresponding to the gate lines and the data lines and thin film transistors, and additionally include a signal applying part for applying a position recognizing signal. Color filters(123) are formed between the black matrices. A liquid crystal layer is formed between the first substrate and the second substrate.

Description

Position sensing liquid crystal display device {POSITION SENSITIVE LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a position sensing liquid crystal display, and more particularly, to an integrated position sensing liquid crystal display without signal interference between the position sensing electrode and the common electrode.

Recently, various display devices having a large screen and high quality, in addition to the CRT (Cathode Ray Tube), have been developed, and there are PDP, LCD, and projection display. Among them, LCDs are widely used with LEDs because of their relatively low manufacturing cost, thin thickness, and low heat generation, and are widely used as electronic wrist watches, TV screen displays, and outdoor full-color displays. .

In general, a liquid crystal display device is composed of a TFT array (thin film transistor-array) substrate 10, a C / F (color filter) substrate 20, and a liquid crystal layer 30 formed therebetween, as shown in FIG. It is.

The TFT substrate 10 has a thin film transistor TFT installed at each pixel and serves as a switching function to apply and block a signal voltage to the liquid crystal, and a signal voltage applied through the thin film transistor TFT to the liquid crystal cell. The pixel electrode 8 to be applied is formed, and the light blocking film 22 formed between the pixels is formed on the C / F substrate 20, and a color including a plurality of red (R), green (G), and blue (B) pixels. The common electrode 28 made of the filter layer 23 and indium tin oxide (ITO) is formed thereon.

On the upper surfaces of the C / F substrate 20 and the TFT substrate 10, alignment films 29 and 9 made of thin organic films made of polyimide are formed.

In addition, a spacer 32 is disposed between the C / F substrate 20 and the TFT substrate 10 so as to inject a liquid crystal so that a space having a predetermined height is formed. The sealant 34 located at the edge of the panel constitutes an active cell region and serves as an adhesive for fixing the C / F substrate 20 and the TFT substrate 10.

Hereinafter, the structure and function of the TFT substrate and the C / F substrate will be described in more detail.

First, the C / F substrate 20 and the color filter 23 of the resin film containing the dye or pigment of the three basic colors of red (R), green (G), blue (B) on the transparent substrate 21 and And an overcoat for planarization of the black matrix 22 of the light blocking layer formed between the pixels of the color filter 23 and the color filter 23 or for improving adhesion to ITO. film 25, a common electrode 28 made of ITO, a transparent electrical conductor formed to apply a voltage to the liquid crystal cell, and an alignment layer 29 formed to align the liquid crystal molecules. A black matrix 22 is formed on the TFT substrate in correspondence with the gate line and data line defining each pixel and the thin film transistor.

In addition, the TFT substrate 10 is formed on the transparent substrate 1 and has a gate electrode 2 to which a scan signal is applied from a gate line (not shown), and a semiconductor layer 4 provided to transmit a data signal in response to the scan signal. ), A gate insulating film 3 that electrically isolates the semiconductor layer 4 and the gate electrode 2, and a source formed on the semiconductor layer 4 to apply a data signal from a data line (not shown). A thin film transistor TFT formed of an electrode 6a and a drain electrode 6b for applying a data signal to the pixel electrode 8 is formed. A passivation layer having a contact hole 11 exposing the drain electrode 6b of the thin film transistor is coated on the entire surface of the thin film transistor and the substrate, and the drain electrode 6b is connected to the pixel electrode 8 through the contact hole 11. Is electrically connected to the The pixel electrode 8 is formed of a transparent electrode made of ITO so that a light beam is transmitted. The active layer of the thin film transistor includes a semiconductor layer 4 formed by depositing amorphous silicon (a-Si) and a semiconductor layer 4. It consists of an n + doped ohmic contact layer 5 on both sides.

When a scan signal having a high level is applied to the gate electrode 2 of the thin film transistor, a channel through which electrons can move is formed in the semiconductor layer 4 so that the data signal of the source electrode 6a is a semiconductor. It is transferred to the drain electrode 6b via the layer 4. On the other hand, when a scan signal having a low level is applied to the gate electrode 2, the channel formed in the semiconductor layer 4 is cut off and the transmission of the data signal to the drain electrode 6b is stopped.

Such a general liquid crystal display device displays only an image by a driving signal applied from the outside. Recently, in order to use it more efficiently, a lot of researches have been conducted to configure a position sensing device in a liquid crystal display device and use it as a note. have. That is, when a character or a picture is drawn by the electronic pen on the liquid crystal display device having the position sensing element, the character or the picture drawn by the electronic pen is displayed on the liquid crystal display as it is.

A position sensitivity device mounted on the liquid crystal display is also called a touch screen or tablet, and may be a resistive film type, a capacitive type, or a magnetic field depending on a method for sensing a position indicated by a user. Are classified in a manner.

The resistive film method detects a position pressed by pressure in a state in which a DC voltage is applied as a change in the amount of current, and the capacitive method senses a capacitance coupling in a state in which an AC voltage is applied. In addition, the magnetic field method detects the selected position as the change of the voltage while the magnetic field is applied.

Recently, an integrated position sensing liquid crystal display device having a position sensing element function in a liquid crystal display device has been developed.

An integrated position sensing liquid crystal display device is made possible by using a black matrix formed on a C / F substrate of a conventional liquid crystal display device as a position sensing electrode.

That is, by using the black matrix 22 formed on the C / F substrate 20 of the liquid crystal display device shown in FIG. 1 as the position sensing electrode, the position sensing function is added to the liquid crystal display device. In order to apply the position sensing signal, a signal applying unit must be separately configured.

FIG. 2 is a plan view showing the C / F substrate of the position sensing liquid crystal display device using the black matrix 22 as the position sensing electrode.

As shown in FIG. 1, a black matrix 22 is formed in a mesh shape corresponding to the gate line and the data line of the TFT array substrate illustrated in FIG. 1, and a red (R) is formed between the black matrix 22. ), Green (G) and blue (B) color filter layers 21 are formed.

In addition, the black matrix 22 is used as a position sensing electrode with a role of blocking light leaking from the gate line, the data line and the thin film transformer, and a signal for applying a position sensing signal to be used as the position sensing electrode. The applicator is configured separately.

Hereinafter, the problem of the conventional position sensing liquid crystal display device will be described through a schematic view of the position sensing liquid crystal display device.

3 is a schematic diagram of a conventional integrated position sensing liquid crystal display device used in a general TN mode for convenience of description. As shown in the drawing, the C / F substrate 20 and the TFT substrate 10, and The liquid crystal layer 30 is formed between the C / F substrate 20 and the TFT substrate 10.

The C / F substrate 20 has a black matrix 22 as a position sensing electrode and a light blocking film on the transparent substrate 21, a color filter 23 formed therebetween, and an overcoat formed to planarize the color filter 23. A film 25 and a common electrode 28 formed thereon.

Although not shown in the drawing, the TFT substrate 10 includes thin film transistors including the gate electrode 2, the source electrode 6a, and the drain electrode 6b at regular intervals, and the drain electrode 6b. A pixel electrode 8 made of a transparent ITO material connected to is formed on the entire surface of the pixel region.

In addition, alignment films 29 and 9 for aligning liquid crystals are formed on opposite surfaces of the C / F substrate 20 and the TFT substrate 10.

The integrated position sensing liquid crystal display device configured as described above displays an image by a voltage between the common electrode 28 and the pixel electrode 8 when a driving signal is applied from external driving circuits.

However, there is a problem in that the position cannot be accurately detected due to noise caused by interference between the position sensing signal applied to the black matrix and the signal applied to the common electrode for position sensing.

In addition, in the overcoat layer 25 formed between the black matrix 22 and the common electrode 28, holes are frequently generated on the film due to process defects, and the black matrix 22 is formed by the generated holes. And a short phenomenon occur between the common electrode 28 and the common electrode 28. This not only deteriorates the image quality by distorting the voltage applied between the liquid crystals, but also makes it difficult to accurately recognize the position.

In addition, a capacitor coupling phenomenon occurs between the black matrix 22 and the common electrode 28 having the overcoat layer 25 interposed therebetween, and a position sensing signal applied to the black matrix 22. Distortion of the Vcom signal due to signal interference between the signals applied to the common electrode 28 causes cross talk on the screen, and it is difficult to realize perfect black at the black level, thereby reducing the contrast ratio. There was a problem letting.

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is a conventional integrated position-aware liquid crystal display in an in-plane switching (IPS) mode in which a common electrode and a pixel electrode are formed on the same substrate. By applying the device, it is possible to provide a position sensing liquid crystal display device having improved position sensing ability and screen quality by preventing short circuit defects and signal interference between a black matrix formed on a C / F substrate and a common electrode.

Other objects and features of the present invention will be described in detail in the configuration and claims of the following invention.

1 is a cross-sectional view showing a cross section of a general liquid crystal display device.

2 is a plan view showing a plane of a color filter substrate in an integrated position sensing liquid crystal display device;

3 is a schematic view of a conventional integrated position sensing liquid crystal display device.

4A to 4B illustrate a first embodiment of an integrated position sensing liquid crystal display device of the present invention.

5 is a second embodiment of an integrated position sensing liquid crystal display of the present invention;

6 is a third embodiment of the integrated position sensing liquid crystal display of the present invention;

*** Explanation of symbols for main parts of drawing ***

102 gate electrode 103 gate insulating film

104: semiconductor layer 105: ohmic contact layer:

106a: source electrode 106b: drain electrode

107: protective film 108: pixel electrode

122: black matrix 128: common electrode

123: color filter 125: overcoat film

In order to achieve the above object, the position sensing liquid crystal display device of the present invention is a C / F substrate including a black matrix and a color filter, a TFT substrate including a common electrode, a pixel electrode, and a thin film transistor (TFT). The black matrices serve as light shields and position sensing electrodes, and meshes between the red (R), green (G), and blue (B) color filters. mesh).

The thin film transistor TFT is formed of a gate electrode, a gate insulating film, a source / drain electrode, and an active layer including a semiconductor layer and an ohmic contact layer.

Since the common electrode and the pixel electrode are formed on the same substrate (TFT substrate), the position sensing liquid crystal display device according to the present invention configured as described above is applied to the coupling phenomenon and the position sensing signal and the common electrode between the black matrix and the common electrode. Interference between signals can be eliminated.

Hereinafter, the position recognition liquid crystal display according to the present invention will be described in detail with reference to the accompanying drawings.

4A and 4B are schematic views of a plane and a cross-sectional view of the position recognition liquid crystal display according to the present invention. As shown in FIG. 4A, gate lines 124 and data arranged vertically and horizontally on the TFT substrate 110 are illustrated. The pixel area is defined by the line 160. Although the actual liquid crystal panel is composed of many pixel areas, only one pixel is shown in the drawing for convenience of description.

A common line 130 parallel to the gate line 124 is arranged in the pixel region 110, and a thin film transistor is formed at the intersection of the gate line 124 and the data line 160. have. As shown in FIG. 4B, the TFT may include a gate electrode 102, a gate insulating layer 103, source / drain electrodes 6a and 6b, a semiconductor layer 104, an ohmic contact layer 105, and a source / drain electrode ( 6a and 6b and is connected to the gate line 124 and the data line 160. In addition, a gate insulating film 103 is applied over the gate electrode 102 and the entire substrate.

The common electrode 128 and the pixel electrode 108 which are parallel to each other are formed in the pixel region. The common electrode 128 is formed on the substrate 101 at the same time as the gate electrode 102 and connected to the common line 140. The pixel electrode 108 is formed on the gate insulating layer 103 by the source / drain electrodes 6a and 6b. Is formed at the same time and is connected to the source / drain electrodes 6a and 6b of the thin film transistor. A protective film 107 and a first alignment film are applied over the entire substrate.

The C / F substrate 120 has a black matrix 122, a color filter 123, and a color, which not only prevent light leakage from the thin film transistor, the gate line 124, and the data line 160, but also serve as position sensing electrodes. An overcoat 125 is formed to planarize the filter, and a second alignment layer 129 is coated thereon. In addition, the liquid crystal layer 130 is formed between the C / F substrate 120 and the TFT substrate 110. Since the black matrix 122 is used as a light blocking film and a position sensing electrode, a separate signal applying unit for applying a position sensing signal is formed.

In the liquid crystal display device having the above structure, when no voltage is applied, the liquid crystal molecules in the liquid crystal layer 130 are aligned in accordance with the alignment directions of the first alignment layer 109 and the second alignment layer 129. When a voltage is applied through the thin film transistor, a transverse electric field parallel to the surface of the substrate is formed between the common electrode 128 and the pixel electrode 108. Since the liquid crystal molecules oriented along the alignment direction of the first alignment layer 109 and the second alignment layer 129 by the transverse electric field are switched horizontally with the substrate 101, the position sensing signal applied to the black matrix 122 is applied to the position detection signal. Regardless, the pixel voltage is applied to the liquid crystal.

In the conventional twisted nematic (TN) mode, since the common electrode and the black matrix are formed on the same substrate with the overcoating layer interposed therebetween, when a signal is applied to the common electrode and the black matrix, coupling occurs between the two electrodes. There is a problem that the common voltage Vcom is distorted. In addition, when a hole is formed in an overcoating layer made of an insulating layer due to a process defect, there is a problem of opening between the common electrode and the black matrix through the hole.

However, in the present invention, by forming the common electrode on the TFT substrate, even if a signal is applied to the common electrode and the black matrix, the common electrode and the black matrix are formed on different substrates, thereby preventing signal interference therebetween. In addition, short circuit defects between the common electrode and the black matrix can be eliminated due to holes formed in the overcoating layer due to process defects.

5 to 6 show other embodiments of the invention.

First, as shown in FIG. 5, the common electrode 128 made of a transparent metal is formed on the passivation layer 107, and the aperture ratio of the common electrode 128 made of an opaque metal and the pixel electrode can be greatly improved. Can be.

6, the common electrode 128 made of a transparent metal is formed on the same plane as the pixel electrode 108 on the gate insulating film 103, so that a voltage between two electrodes (common electrode / pixel electrode) When applied, the generation of transverse electric charges completely parallel to the surface of the substrate makes it possible to further improve the viewing angle as compared with the first and second embodiments.

In the second and third embodiments, the transparent metal used as the common electrode is made of indium tin oxide (ITO).

As described in the above embodiments, since the common electrode and the pixel electrode are formed on the same substrate, the interference between the signal applied to the black matrix (position sensing electrode) and the signal applied to the common electrode for position sensing By removing the noise by removing the noise, not only the position sensing ability can be improved but also the distortion of the common voltage Vcom can be prevented to improve the screen quality.

As described above, according to the present invention, the integrated position sensing liquid crystal display device used in the conventional TN mode is applied to the IPS mode, so that the B / M (position sensing electrode) and the common electrode formed on the same substrate with an overcoating layer therebetween. The position sensing ability can be improved by removing the noise due to short circuit and signal interference, and it is possible to prevent the contrast deterioration due to the distortion of the common voltage.

Claims (11)

In an integrated position sensing liquid crystal display device using a black matrix as a position sensing electrode, First and second substrates; Gate and data lines arranged vertically and horizontally on the first substrate to define pixel regions; A thin film transistor formed at the intersection of the gate and the data line; At least a pair of first and second metal layers formed in the pixel region; A protective film laminated on the first substrate; A black matrix formed at a corresponding position of the gate / data line and the thin film transistor on the second substrate and further including a signal applying unit for applying a position recognition signal; A color filter formed between the black matrices; And a liquid crystal layer formed between the first and second substrates. The thin film transistor of claim 1, wherein the thin film transistor comprises: a gate electrode connected to the gate line; A gate insulating film stacked on the gate electrode; A semiconductor layer formed on the gate insulating film; An ohmic contact layer formed on the semiconductor layer; And a source / drain electrode formed on the ohmic contact layer and connected to the data line. The position sensing liquid crystal display device according to claim 1, further comprising a common line formed in the pixel region. The liquid crystal display of claim 1, wherein the first metal layer is a common electrode and the second metal layer is a pixel electrode. The liquid crystal display of claim 1, wherein the first metal layer is indium tin oxide (ITO). The liquid crystal display of claim 1, wherein the first metal layer is made of an opaque metal. The position sensing liquid crystal display of claim 1, wherein the first metal layer and the second metal layer are formed on the same plane. 8. The position sensing liquid crystal display device according to claim 7, wherein the first metal layer and the second metal layer are formed on a gate insulating film. 2. The position sensing liquid crystal display device according to claim 1, wherein the first metal layer and the second metal layer are formed on different planes. The liquid crystal display of claim 1, wherein the first metal layer is formed on the passivation layer, and the second metal layer is formed on the gate insulating layer. The position sensing liquid crystal display of claim 1, further comprising an alignment layer coated on the entire surface of the first and second substrates.